Get your facts straight MARKHAM

I have been a client of Markham for 7 years and every month have made the correct payments and in due time. October 2019 I even made a huge payment on my account. Now I have received my statement which said only R280 are due by the 1st so I have made my payment of that exact amount. Now this morning 05/05 Markham legal department phones me and tries to threaten me and tell me I haven't made the payment of over 1k which is absurd because how can my statement say one amount and then all of a sudden they have a different amount on the system after I have paid them the amount which my statement showed!!! You trying to do pathetic tricks during this Epidemic to rob and do people in!! Please explain to me how can the amount in 7 years now all of a sudden differ from the one on the statement!?